In various types of current digital communication such as terrestrial digital broadcasting, IEEE802.11a and the like, orthogonal frequency division multiplexing (OFDM) has been widely adopted as a transmission method.
An exemplary OFDM receiver generates reliability information by using calculated noise power, and utilizes the reliability information to enable high-accuracy error correction using an LDPC (Low Density Parity Check) code (for example, PTL 1). According to the technique disclosed in PTL 1, specifically, for noise power calculated from pilot signals or an OFDM band spectrum, average noise power in a symbol direction is compared with noise power in each symbol, and in the case where the noise power in each symbol exceeds a predetermined threshold, it is determined that impulse interference exists, and a value of the noise power in each symbol is used to generate the reliability information. On the contrary, in the case where the noise power in each symbol does not exceed the predetermined threshold, it is determined that the impulse interference does not exist, and a value of the average noise power in the symbol direction is used to generate the reliability information. Thereby, even when the noise power locally increases, proper reliability information can be generated, improving an LDPC decoding performance. However, PTL 1 fails to mention a specific method of calculating the noise power in units of symbol.
Here, the impulse interference means an irregular and random interference signal. Since impulse noise occurs in an impulse manner from, for example, power-ON/OFF of household electrical appliances, lighting equipment or automobile ignition, the noise power locally increases in the symbol in which the impulse noise exists.
There is a method of estimating the noise power existing in each symbol, which is necessary for estimating the reliability information (for example, PTL 2). PTL 2 describes that, in ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) as Japanese terrestrial digital broadcasting, either or both TMCC (Transmission Multiplexing Configuration Control) signals and AC (Auxiliary Channel) signals, which are continuously inserted into a predetermined subcarrier in a time direction are used to estimate the reception quality.